Removal Processes of Volcanic Ash Particles from the Atmosphere

INTRODUCTION The use of satellite techniques provides valuable information for mapping ash hazards, as well as the means to study and predict the fates of volcanic clouds. We have used ultraviolet (TOMS – Total Ozone Mapping Spectrometer) and infrared (e.g., AVHRR – Advanced Very High Resolution Radiometer; HIRS2 – High Resolution Infrared Radiation Sounder/2; GOES – Geostationary Operational Environmental Satellite; MODIS – Moderate Resolution Imaging Spectroradiometer) satellite sensors to examine the solid, liquid and gas species in numerous volcanic clouds over the past 25 years. Each sensor provides a somewhat different perspective of volcanic clouds, depending on their spatial, spectral and temporal resolutions. Thus, when combined these techniques provide important constraints on the interactions and fates of species within the clouds. Quantitative infrared techniques can provide information on how the size, size distribution, and total mass of fine ash particles evolve as a cloud mixes with the atmosphere. Here we present a review of past relevant observations and research, and the results of ongoing satellite studies.